1. Field of the Invention
The present invention relates to a water quality measuring device having a reagent supply unit.
2. Description of Related Art
There is known a measuring device that measures dissolved oxygen concentration, hardness, pH, residual chlorine concentration, and the like of supply water to boilers and service water and drainage water to cooling towers and various other water treatment plants by adding a predetermined medicine to sample water obtained in a cell, and detecting a change of the sample water caused by the addition of the medicine as a change in intensity of transmitted light.
With this type of measuring devices, an improvement of medicine adding devices have been made for use in automatic measurement. For example, such a device and a mechanism are conventionally known as an adding device including a medicine cartridge, and an adding mechanism for gradually adding a medicine from the medicine cartridge to sample water in a cell. In those device and mechanism, the medicine cartridge is provided with a medicine package housed within a case, and the medicine package includes a container for containing a fluid medicine, a tube body (connecting unit) for connecting an exterior and an interior of the container, and a tube made of an elastic material connected to the tube body on one end and having a nozzle for discharging the medicine on the other end. The adding mechanism is configured to pull out the tube by rotating a pressing roller to cause the medicine to flow from the container into the tube through the tube body, and to discharge the medicine through the nozzle.
The container used for the medicine package is a molded product made of a resin material such as a polypropylene resin or a polyethylene resin, and maintains a certain shape. Therefore, in order to stably discharge the medicine through the nozzle of the tube by the adding mechanism, it is necessary to provide the container with an inlet for external air. However, external air flowing into the container through the inlet may possibly denature the medicine within the container. For example, in the measurement of dissolved oxygen concentration and residual chlorine concentration of the sample water, it is necessary to add a redox coloring reagent as a medicine to the sample water. However, when this type of coloring reagent is exposed to external air, the reagent itself is oxidized-reduced. Therefore, an application of redox medicines to the adding device described above is practically difficult.